// Copyright (c) 1995-2009 Nokia Corporation and/or its subsidiary(-ies).

// All rights reserved.

// This component and the accompanying materials are made available

// under the terms of the License "Eclipse Public License v1.0"

// which accompanies this distribution, and is available

// at the URL "http://www.eclipse.org/legal/epl-v10.html".

//

// Initial Contributors:

// Nokia Corporation - initial contribution.

//

// Contributors:

//

// Description:

// e32\euser\maths\um_asin.cpp

// Arc sin.

// 

//

#include "um_std.h"

#if defined(__USE_VFP_MATH) && !defined(__CPU_HAS_VFP)

#error	__USE_VFP_MATH was defined but not __CPU_HAS_VFP - impossible combination, check variant.mmh 

#endif

#ifndef __USE_VFP_MATH

LOCAL_D const TUint32 ArcsinCoeffs[] =

	{

	0x00000000,0x80000000,0x7FFF0000,	// polynomial approximation to arcsin(x)

	0xAA893CD8,0xAAAAAAAA,0x7FFC0000,	// for -0.5<=x<=0.5

	0xD07ED410,0x99999999,0x7FFB0000,

	0xB6C64A72,0xB6DB6D94,0x7FFA0000,

	0xF5527DD4,0xF8E3995C,0x7FF90000,

	0xA87499FB,0xB744B969,0x7FF90000,

	0x2E8953AD,0x8E392B24,0x7FF90000,

	0xFEDBB4E4,0xE3481C4A,0x7FF80000,

	0x4A32ED70,0xC89998E1,0x7FF80000,

	0x848A2B53,0xCCAE4AE5,0x7FF70000,

	0x09C1F387,0xA587A043,0x7FF90000,

	0x722B9041,0x8C9BD20B,0x7FF90001,

	0xC88B75CC,0x850CE779,0x7FFA0000

	};

LOCAL_D const TUint32 Onedata[] = {0x00000000,0x80000000,0x7FFF0000};		// 1.0

LOCAL_D const TUint32 Halfdata[] = {0x00000000,0x80000000,0x7FFE0000};		// 0.5

LOCAL_D const TUint32 Pidata[] = {0x2168C235,0xC90FDAA2,0x80000000};		// pi

LOCAL_D const TUint32 PiBy2data[] = {0x2168C235,0xC90FDAA2,0x7FFF0000};		// pi/2

LOCAL_C TInt CalcArcsinArccos(TReal& aTrg, TRealX& x, TBool aCos)

	{

	//	Calculate arcsin (if aCos false) or arccos (if aCos true) of x

	//	and write result to aTrg.

	//	Algorithm (arcsin):

	//		If x>0.5, replace x with Sqrt((1-x)/2)

	//			( use identity cos(x)=2(cos(x/2))^2-1 )

	//		Use polynomial approximation for arcsin(x), 0<=x<=0.5

	//		If original x>0.5, replace result y with pi/2-2y

	const TRealX One = *(const TRealX*)Onedata;

	const TRealX Half = *(const TRealX*)Halfdata;

	const TRealX Pi = *(const TRealX*)Pidata;

	const TRealX PiBy2 = *(const TRealX*)PiBy2data;

	TInt sign=x.iSign&1;

	x.iSign=0;

	if (x<=One)

		{

		TBool big=(x>Half);

		if (big)

			{

			x=One-x;

			if (x.iExp>1)

				x.iExp--;

			TReal temp;

			Math::Sqrt(temp, (TReal)x);

			x=temp;

			}

		TRealX y;

		Math::PolyX(y,x*x,12,(const TRealX*)ArcsinCoeffs);

		y*=x;

		if (big)

			{

			if (y.iExp)

				y.iExp++;

			if (aCos)

				{

				if (sign)

					y=Pi-y;

				}

			else

				{

				y=PiBy2-y;

				y.iSign=TInt8(sign);

				}

			}

		else

			{

			y.iSign=TInt8(sign);

			if (aCos)

				y=PiBy2-y;

			}

		return y.GetTReal(aTrg);

		}

	return KErrArgument;

	}

EXPORT_C TInt Math::ASin(TReal& aTrg, const TReal& aSrc)

/**

Calculates the principal value of the inverse sine of a number.

@param aTrg A reference containing the result in radians,

            a value between -pi/2 and +pi/2. 

@param aSrc The argument of the arcsin function, a value

            between -1 and +1 inclusive.

@return KErrNone if successful, otherwise another of the system-wide

        error codes.

*/

	{

	TRealX x;

	TInt r=x.Set(aSrc);

	if (r==KErrNone)

		r=CalcArcsinArccos(aTrg,x,EFalse);

	if (r==KErrNone)

		return r;

	SetNaN(aTrg);

	return KErrArgument;

	}

EXPORT_C TInt Math::ACos(TReal& aTrg, const TReal& aSrc)

/**

Calculates the principal value of the inverse cosine of a number.

@param aTrg A reference containing the result in radians,

            a value between 0 and pi. 

@param aSrc The argument of the arccos function, a value

            between -1 and +1 inclusive. 

@return KErrNone if successful, otherwise another of the system-wide

        error codes.

*/

	{

	TRealX x;

	TInt r=x.Set(aSrc);

	if (r==KErrNone)

		r=CalcArcsinArccos(aTrg,x,ETrue);

	if (r==KErrNone)

		return r;

	SetNaN(aTrg);

	return KErrArgument;

	}

#else // __USE_VFP_MATH

// definitions come from RVCT math library

extern "C" TReal asin(TReal);

extern "C" TReal acos(TReal);

EXPORT_C TInt Math::ASin(TReal& aTrg, const TReal& aSrc)

	{

	aTrg = asin(aSrc);

	if (Math::IsFinite(aTrg))

		return KErrNone;

	SetNaN(aTrg);

	return KErrArgument;

	}

EXPORT_C TInt Math::ACos(TReal& aTrg, const TReal& aSrc)

	{

	aTrg = acos(aSrc);

	if (Math::IsFinite(aTrg))

		return KErrNone;

	SetNaN(aTrg);

	return KErrArgument;

	}

#endif